A vaccine prepared by subjecting Vibrio cholerae to low-speed shear contained a mixture of flagella and a vesicular material believed to be fragments of the sheath and possibly the cell wall passively protected infant mice of actively immunized mothers. A dose of 1 microgram protected against challenge with 1000 LD50 of homologous and heterologous serotypes. This vaccine is to be used in adult rabbits to determine whether it protects isolated ileal loops against fluid accumulation and passively protects infant rabbits against direct intraintestinal challenge. To be included in thse studies is a scanning electron microscopic examination of the ileal mucosa of infant mice, infant rabbits and adult rabbits to determine whether a difference in association of vibrios with mucosal cells can be related to the immune status of the host. Since it is likely that receptor-sites on the mucosal cells are similar to those on type O erythrocytes, attempts will be made to block vibrio attachment with ghosts of this type of red blood cell.